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Evensong at St. Paul's Cathedral: Why Nature is ultimately unfathomable—and why reverence towards it is the only sensible attitude

In the 17th and 18th centuries the greatest scientists and artists from Isaac Newton to Johann Sebastian Bach were wont to declare that the only proper use for their God given intellect was the better to appreciate the works of God. Christopher Wren was among the greatest intellectuals of them all and this building is among the finest expressions of that idea.

But science changed its tone in the centuries after Newton. When I read science at university in the early 1960s it seemed to be widely assumed that we, humanity, were on the point of complete understanding; and what we could understand, we could and should control, for our own benefit. Prime Minister Harold Wilson spoke of “the white heat of technology”. President Nixon urged, “Let's lick cancer in the sixties!” President Kennedy wanted Americans to get to the moon—and they succeeded; thus reinforcing the idea that we really can do anything we set our minds to; that we really can take charge of the world. This idea was encapsulated in one grand slogan: “The conquest of nature”.

But of all humanity's conceits, the idea that we can understand nature, and indeed that we can “conquer” it, or that that is a good idea, is perhaps the most ludicrous and chilling of all. Those who understand most of how life works are the ones who realise how little we know.

We don't even know how many kinds of creatures there are—how diverse biodiversity really is. So far biologists have listed around two million different species. But about 30 years ago an American scientist counted all the beetles in one fairly ordinary tree in Panama and found 1100 species of them, many of which were new to science; and beetles are only one group among many—what about the mites and worms and fungi and goodness knows what else. From all this he concluded that in the world as a whole there could be 30 million different species—but that's not counting microbes, of which there could be hundreds of millions of kinds. Now most biologists feel that he may have got carried away, and there are probably (only!) between five and eight million. But we don't know. We are no-where knowing.

Of course, beetles are small and microbes are even smaller, and we might be forgiven for overlooking them. But I have been looking at trees of late and although you might think it's difficult to miss a tree, the picture is not much better there. We can be fairly sure about our own country. Britain seems to have 39 native species of tree, and that's it. But most trees, like most of everything, live in the tropics. Tree biologists estimate that in the American tropics alone, from Mexico through Brazil to Argentina and Chile, there are probably around 30,000 kinds of tree. But it's just a guess. There can be 300 different species in any one hectare, and all you can see of them is their bark because the leaves and fruits are way up in the gloom, and there are different species in different regions. We just don't know how many there are in all.

But what really matters is how all these myriad creatures live their lives, and how they interact with each other, and with the physical world: not the cast list, but the plot. And although the modern science of ecology is wonderful, all we have so far is glimpses; yet each glimpse is a revelation.

What is becoming clear—one of the most important of those revelations—is that although biologists have stressed the significance of competition in nature—“nature red in tooth and claw” as Tennyson put the matter—and of course the entire modern economy is built on competition—life is at least as cooperative as it is competitive. Some of the creatures that live in and around any one tree are indeed competing with that tree—they are there to eat it—but many others are vital to its own survival. Pines grow well on very poor soils—but only because they have fungi in their roots, known as mycorrhizae, that help to draw nourishment from the soil. Actually, most trees have mycorrhizae. In fact it's very likely that plants could not have ventured on to land at all at all if they hadn't first teamed up with fungi, in symbiotic relationships.

Tropical trees in particular need birds and insects to spread their pollen. Figs are pollinated by tiny wasps. 750 different species of fig are known and each and every one of them, all 750, has its own particular species of wasp. When the fruits are ripe, another suite of animals is on hand to scatter the seed. Figs rely on fruit bats—little figs for little bats, and big figs for big bats. Some require a whole sequence of animals. I know a tree in Panama that needs monkeys to scatter its seed, which must then be buried by oversized guinea pigs known as pacas. But the pacas return later to eat the seeds—and the system would fail were it not for the ocelots, the local spotted cats, who eat a lot of the pacas before they have time to dig the seeds up. No ocelots, no seeds, no trees. Who'd have thought that trees need cats? As a former dean of this place once famously commented, “No man is an island”; and for “man” read tree, or monkey, or fungus, or anything else.

But why should we bother with all this, except for whimsy? One example will do. A few years ago there was a huge rainstorm over London. The drains couldn't cope. Six million gallons of effluent went straight into the Thames. This surely will happen more and more as global warming starts to bite. Engineers have a solution. Catch as much rain as possible in water-butts. Make porous pavements and car-parks, so the water soaks away. In short: hold up the water; slow the flood; make sure it doesn't all hit the ground at the same time.

But what civil engineers can do in one small town at a cost of billions, trees do the world over for free. Trees can catch half the rainfall in their leaves before it hits the ground—and evaporate half of what they catch like washing on a line so it doesn't reach the ground at all. Their roots make channels into the earth so it's easy for the water to soak away. Then they can drag the water up again—500 gallons a day for a big tree on a warm day: swimming baths full from a small park. But then they can bring the water back down again. Forest trees send organic vapours into the air that act as seed clouds, and so they can lay on their own rain supply. Now that really is clever. It's way out of our league.

Still, though, some scientists seem to think that if only they do enough research, they will understand it all one day. Omniscience is just over the next hill. Politicians and industrialists are happy to take them at their word, and continue to knock the world about, felling forests and draining marshes and re-directing rivers in the cause of economic growth, as if they knew what they were doing.

They should take note, first of all, of John Stuart Mill, who pointed out 150 years ago that however much we know, there might always be something around the next corner that we haven't thought of. All we can be sure of at any one time is that we don't know it all. Furthermore, we can never know how much we don't know. It's Catch 22. It would be logically impossible to gauge the extent of our own ignorance unless we were already omniscient.

They should also take note—we should all take note—of the core morality of all the great religions. All their great founders stressed that morality rests on attitude; and the attitudes that really matter, on which all else is founded, are those of personal humility, respect for other creatures, and reverence for nature as a whole.

Science is wonderful and it is necessary, but it has not brought us omniscience and it never can. In fact its greatest lesson has been that nature is beyond our ken. To approach nature with humility and to treat it with respect and reverence isn't just a matter of piety. It is the only sensible survival strategy.